Differential Involvement of the P2Y1 and P2YT Receptors in the Morphological Changes of Platelet Aggregation

Eckly, Anita; Gendrault, Jean-Louis; Hechler, Béatrice; Cazenave, Jean‐Pierre; Gachet, Christian

doi:10.1055/s-0037-1615655

Cited by 55 publications

(74 citation statements)

References 27 publications

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“…8,9 Full integrin activation with ADP requires the P2Y 1 and P2Y 12 purinergic receptors. 10,11 Recent studies show that integrin ␣2␤1 can also be activated by inside-out signaling. 12,13 Thrombin and collagen turn this integrin into a high-affinity form, whereas ADP changes it to intermediate affinity.…”

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confidence: 99%

Principal Role of Glycoprotein VI in α2β1 and αIIbβ3 Activation During Collagen-Induced Thrombus Formation

Lecut

Schoolmeester

Kuijpers

et al. 2004

ATVB

112

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Objective-High-shear perfusion of blood over collagen results in rapid platelet adhesion, aggregation, and procoagulant activity. We studied regulation of ␣2␤1 and ␣IIb␤3 integrin activation during thrombus formation on collagen. Methods and Results-Blockade of glycoprotein (GP) VI by 9O12 antibody or of P2Y purinergic receptors permitted platelet adhesion but reduced aggregate formation, fibrinogen binding, and activation of ␣2␤1 and ␣IIb␤3, as detected with antibodies IAC-1 and PAC1 directed against activation-dependent epitopes of these integrins. Combined blockade of GPVI and P2Y receptors and thromboxane formation abolished integrin activation but still allowed adhesion of morphologically unstimulated, nonprocoagulant platelets. Exogenous ADP partly restored the suppressive effect of GPVI blockade on integrin ␣2␤1 and ␣IIb␤3 activation. Adhesion was fully inhibited only with simultaneous blocking of GPVI and ␣2␤1, indicating that the integrin can support platelet-collagen binding in the absence of its activation. Blockade or absence of GPIb␣ only moderately influenced integrin activation and adhesion unless GPVI was inhibited. Conclusions-GPVI-and autocrine-released ADP induce affinity changes of ␣2␤1 and ␣IIb␤3 during thrombus formation on collagen under flow. These integrin changes are dispensable for adhesion but strengthen platelet-collagen interactions and thereby collagen-induced platelet activation. Key Words: ADP Ⅲ collagen Ⅲ glycoprotein VI Ⅲ integrins Ⅲ platelets Ⅲ thrombus P latelet integrins are critical in hemostasis. Abundantly expressed at the platelet surface, integrins are required for platelet interactions with subendothelial matrix components and for platelet-platelet interactions leading to aggregate and thrombus formation. 1 Integrin ␣2␤1 plays a role in platelet adhesion to collagen under static 2,3 and flow conditions. 4,5 Integrin ␣IIb␤3 allows platelets to bind to fibrinogen and von Willebrand factor (vWF) present on collagen and other platelets. 6 This leads to stable platelet adhesion and aggregate formation. 7 On resting platelets, these integrins are considered to be present in a low-affinity state. Intracellular signaling or ligand binding results in conformational changes of the integrins with a switch to higher-affinity states. 6 Agonists such as thrombin, collagen, ADP, and vWF induce ␣IIb␤3 activation and platelet aggregation. 8,9 Full integrin activation with ADP requires the P2Y 1 and P2Y 12 purinergic receptors. 10,11 Recent studies show that integrin ␣2␤1 can also be activated by inside-out signaling. 12,13 Thrombin and collagen turn this integrin into a high-affinity form, whereas ADP changes it to intermediate affinity. 13 Although much is known of the affinity and avidity changes of ␣IIb␤3 on isolated platelets especially, 8,14 regulation of integrin activation during thrombus formation is incompletely understood.In vivo studies as well as ex vivo experiments, in which blood was allowed to flow over collagen under arterial shear conditions, have indicated that glycop...

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mentioning

confidence: 99%

Principal Role of Glycoprotein VI in α2β1 and αIIbβ3 Activation During Collagen-Induced Thrombus Formation

Lecut

Schoolmeester

Kuijpers

et al. 2004

ATVB

112

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“…In human platelets, GPVI-mediated Rap1 activation is largely dependent on secreted ADP and specifically requires signaling through the P2Y 12 ADP receptor, a receptor that is critical for the formation of stable platelet aggregates. 37 The connection between a collagen receptor necessary for platelet responsiveness to the extracellular matrix, an ADP receptor critical for stable platelet aggregate formation, and a small GTPase that is readily activated by a number of platelet agonists 22 suggests a mechanism by which platelets can coordinate a number of different activation signals.The discovery that ADP signaling is critical for complete Rap1 activation by GPVI is an intriguing finding. Previous studies indicated that thrombin-induced Rap1 activation was not dependent on ADP because ADP scavengers failed to inhibit Rap1 activation.…”

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confidence: 99%

Identification of P2Y12-dependent and -independent mechanisms of glycoprotein VI–mediated Rap1 activation in platelets

Larson

Chen

Kahn

et al. 2003

Blood

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Glycoprotein (GP) VI is a critical platelet collagen receptor, yet the steps involved in GPVI-mediated platelet activation remain incompletely understood. Because activation of Rap1, an abundant small guanosine triphosphatase (GTPase) in platelets, contributes to integrin ␣ IIb ␤ 3 activation, we asked whether and how GPVI signaling activates Rap1 in platelets. Here we show that platelet Rap1 is robustly activated upon addition of convulxin, a GPVI-specific agonist. Using a reconstituted system in RBL-2H3 cells, we found that GPVI-mediated Rap1 activation is dependent on FcR␥ but independent of another platelet collagen receptor, ␣ 2 ␤ 1 . Interestingly, GPVI-mediated Rap1 activation in human platelets is largely dependent on adenosine diphosphate (ADP) signaling through the P2Y 12 and not the P2Y 1 receptor. However, experiments with specific ADP receptor antagonists and platelets from knockout mice deficient in P2Y 1 or the P2Y 12 -associated G-protein, G␣i 2 , indicate that human and murine platelets also have a significant P2Y 12 -independent component of GPVImediated Rap1 activation. The P2Y 12 -independent component is dependent on phosphatidylinositol 3-kinase and is augmented by epinephrine-mediated signaling. P2Y 12 -dependent and -independent components are also observed in GPVImediated platelet aggregation, further supporting a role for Rap1 in aggregation. These results define mechanisms of GPVImediated platelet activation and implicate Rap1 as a key signaling protein in GPVI IntroductionCollagen is a major component of the subendothelial matrix and atherosclerotic plaques and is a potent platelet agonist that contributes to thrombus formation upon plaque rupture. Collagenmediated platelet activation results from a complex set of signals initiated by the coordination of platelet surface proteins, including the immunoglobulin superfamily receptor glycoprotein (GP) VI, the integrin ␣ 2 ␤ 1 , and most recently, GPV. [1][2][3] Activation of GPVI causes the assembly of distinct proximal signaling pathways. GPVI is constitutively associated with FcR␥, a protein containing an immunoreceptor tyrosine-based activation motif. 4,5 Upon collagen ligation to GPVI, FcR␥ becomes phosphorylated by a Src family kinase, 6,7 which subsequently allows the recruitment of other signaling proteins such as Syk, Bruton tyrosine kinase, and phospholipase C␥. [6][7][8][9][10][11] GPVI-mediated signaling is absolutely required for collageninduced platelet aggregation. Human platelets lacking GPVI, but expressing ␣ 2 ␤ 1 , fail to aggregate in response to collagen. 12 In addition, GPVI antagonists inhibit collagen-mediated aggregation. 13 Although human platelets lacking ␣ 2 ␤ 1 also fail to aggregate in response to collagen, 14 fibrillar collagen-mediated platelet aggregation still occurs in ␤ 1 -deficient murine platelets that express GPVI. 15,16 Additionally, GPVI signaling itself can activate ␣ 2 ␤ 1 function. 15 This finding suggests that not only is GPVI a key signaling component of collagen-mediated platelet activation, ...

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“…Platelets possess at least two P2Y receptors whose combined action is required for full activation and aggregation in response to ADP [17][18][19][20][21][22][23] (Fig. 1).…”

Section: The Platelet P2y 1 and P2y 12 Receptors For Adp Intracellulamentioning

confidence: 99%

The Platelet ATP and ADP Receptors

Oury

Tóth-Zsámboki

Vermylen

et al. 2006

CPD

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Adenine nucleotides, ADP and ATP, are coreleased from dense granules during platelet activation, as well as from endothelial cells and damaged red blood cells following vascular injury. Through autocrine and paracrine mechanisms, these extracellular signaling molecules interact with the platelet P2 receptors to amplify ongoing platelet activation. Two receptors for ADP, the G q -protein-coupled P2Y 1 and G i -protein-coupled P2Y 12 and one receptor for ATP, the P2X 1 ion channel, have been identified on platelets. Due to distinct pharmacological properties and differential regulation, the P2Y and P2X receptors essentially operate on different scales of time and distance and trigger selective intracellular signaling cascades. Recent advances in the understanding of the P2Y receptor physiology have reinforced the concept of these receptors as useful targets for antithrombotic therapy. The function of P2X 1 in platelet activation only recently started to be unraveled. This review focuses on recent findings on the physiology of these platelet ADP and ATP receptors, their distinct downstream intracellular signaling pathways as well as on the available agonists, antagonists and inhibitors that allow their pharmacological discrimination.Key Words: Hemostasis, thrombosis, adenine nucleotides, P2Y 1 , P2Y 12 , P2X 1 , antithrombotic therapy. HISTORY AND CLASSIFICATION OF PURINERGIC RECEPTORSThe first report about the potent actions of an adenine compound, AMP, extracted from heart muscle, was published by Drury and Szent-Györgyi in 1929. Initial investigations focused on effects of adenosine and ATP on the heart and vasculature, or concerned the effects of purines on platelets [1] and on mast cells. Further insights into the physiological role of extracellular purines and pyrimidines were provided via the study of their biological sources [2]. In this respect, the detection of nucleotide release from the heart during hypoxia [3] or from skeletal muscle during contraction indicated that secretion of purine compounds might be coupled to metabolic demand to regulate local blood flow. ATP release from sensory nerves suggested that adenine nucleotides play a role as neurotransmitter or neuromodulator in the central and peripheral nervous system [4].These early publications established that purinergic nucleotides act as extracellular signaling molecules [5]. Nucleotides are now documented to contribute to a diverse range of physiological responses such as smooth muscle contraction, neurotransmission, exocrine and endocrine secretion, immune response, inflammation, platelet aggregation, male reproduction, nociception and modulation of cardiac function [6].Purines and pyrimidines mediate their effects by interacting with distinct cell-surface receptors. Purinergic receptors were first formally recognized by Burnstock in 1978 [7]. They were divided into two classes: at P1-purinoceptors adenosine is the principal natural ligand, while P2-purinoceptors recognize both purine and pyrimidine nucleotides Based on an increasin...

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Differential Involvement of the P2Y1 and P2YT Receptors in the Morphological Changes of Platelet Aggregation

Cited by 55 publications

References 27 publications

Principal Role of Glycoprotein VI in α2β1 and αIIbβ3 Activation During Collagen-Induced Thrombus Formation

Principal Role of Glycoprotein VI in α2β1 and αIIbβ3 Activation During Collagen-Induced Thrombus Formation

Identification of P2Y12-dependent and -independent mechanisms of glycoprotein VI–mediated Rap1 activation in platelets

The Platelet ATP and ADP Receptors

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